1. Field of the Invention
The present invention generally relates to a write control apparatus and an image forming apparatus therewith, and a write control method.
2. Description of the Related Art
As an image forming apparatus including a printer, a copier, a facsimile machine, and a multifunction peripheral which has multiple functions thereof, an electrophotography type image forming apparatus is often used. In this type of image forming apparatus, in the case where images are continuously formed on multiple pages, productivity is increased by making a space between transfer sheets (between-sheets distance) as short as possible in order to speed up the image forming process.
Most of today's electrophotography type image forming apparatuses are digital. Digitized image data is processed by a write control apparatus and an exposure apparatus which has a light source such as a laser diode is operated. According to the exposure apparatus, a latent image is formed on a surface of a charged photoconductor by light writing. The electrostatic latent image is developed with toner. The toner image is directly, or via an intermediate transfer member, transferred onto a recording medium such as a transfer sheet. The transferred image is fixed on the recording medium by a fixing device.
In this type of image forming apparatus, in the case where images are continuously formed on multiple pages using various sizes of transfer sheets and using various image formation modes, parameters such as image formation conditions, etc., corresponding to the various sizes and various modes must be set for each page in a write control unit.
In a tandem image forming apparatus used for a color image forming apparatus, in a function of setting parameters in a write control unit from a CPU controlling an engine unit, in order to update the parameters between pages (between-pages period), a high processing speed is required. In order to achieve the high processing speed, a parameter control technique is known in which two sets of the same parameters are respectively set in two sets of registers and only a register selection signal is switched between the pages (double register system).
For example, Patent Document 1 discloses that, in a write control apparatus for writing image information onto paper, a storage unit for setting various parameters necessary for write control and a plurality of storage unit groups (registers) are provided, and the storage unit groups are switched according to print modes.
The parameter setting according to the above-described conventional double register system will be briefly described referring to FIG. 7.
In the system, registers a and registers b which have respective addresses and which have the same function are prepared. Further, for example, in (example 1) of FIG. 7, parameters for A4 size copy are set in the registers a, and parameters for A3 size copy are set in the register b. In (example 2), parameters for A4 size copy are set in the registers a, and parameters for A4 size printer are set in the registers b.
Arrows in FIG. 7 indicate a direction of transfer sheet flow (sub-scanning direction). Further, “copy” means an image formation mode for performing writing using image data read by a scanner from an original image, and “printer” means an image formation mode for performing writing using print data created by an external apparatus such as a personal computer.
Further, just before forming an image of a page whose page size or image formation mode is different, by controlling only a switching register which switches between the registers a and the registers b, registers to be applied to the image formation can be instantly selected.
For example, in (example 2) of FIG. 7, during an image formation of A4-printer in which parameters set in the registers b are applied, parameters for A4-copy are set in the registers a. Then, just before the start of image formation of A4-copy, by setting the switching register to the registers a, an image formation of A4-copy in which parameters set in the registers a are applied can be started.
In this kind of double register system, addresses of the registers a and the registers b are alternated.
In this kind of double register system, in the case of an abnormal end, it may become indefinite which of the registers a and the registers b are effective registers. As a result, at the time of the abnormal end, the switching register must be immediately updated to set one of the registers and the system should restart.
In the parameter control technique according to this kind of conventional double register system, a timing of setting the selection signal needs to be between pages. As a result, a process for monitoring a between-pages timing is needed. In the monitoring process, an active signal which indicates an image formation period and an interrupt signal which indicates an end of the image formation are detected by a CPU.
In order to perform this monitoring process, a high-speed processing function is demanded, such as connecting signal lines and completing the parameter setting process from when an interruption is detected to when the interval between pages (between sheets) ends, which makes the system complex.
Furthermore, in order to secure enough time for setting parameters, the space between pages needs to be increased, which decreases the productivity of the image forming apparatus.
Furthermore, the setting values of a plurality of the same parameters are stored, and therefore an enormous number of selection addresses of storage units need to be controlled from the CPU, which makes the system complex.
Patent Document 1: Japanese Laid-Open Patent Publication No. 2006-259360